<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>消失的边界线</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }

        li{
            list-style: none;
        }

        .ul-containner{
            width: 240px;
            height: 100px;
            margin: 100px auto 0 auto;
            background-color:#eee;
        }

        .ul-containner ul{
            height: 100%;
        }

        .ul-containner li{
            float: left;
            width: 79px;
            height: 20px;
            text-align: center;
            margin-top: 10px;
            border-right: 1px solid #000;
        }

         /* 让3的倍数的li 去掉右边框 */
        .ul-containner li:nth-child(3n){
            border-right: none;
        }

    </style>
</head>
<body>
    <div class="ul-containner">
        <ul>
            <li>测试</li>
            <li>消失</li>
            <li>边界线</li>
            <li>右侧</li>
            <li>边界线</li>
            <li>消失</li>
            <li>测试</li>
        </ul>
    </div>
</body>
</html>

